(CNN) -- California's use of a three-drug combination in executing prisoners was declared invalid Friday by a Marin County judge, who ruled that a one-drug method should have been considered.
"The failure to discuss the one-drug method is a particularly significant omission, since use of a barbiturate-only protocol was raised by at least one commenter," wrote Marin County Judge Faye D'Opal in a nine-page ruling, referring to concerns raised during a public-comment period. Citing one of the three drugs used in the combination, she added, "several commenters make the identical assertion that use of pancuronium bromide is unnecessary, dangerous, and creates a risk of excruciating pain." Pancuronium bromide is a painkiller and muscle relaxant that induces paralysis.
D'Opal further noted that the Department of Corrections failed "to provide a sufficient rationale for rejecting these alternatives" and failed to explain "why a one-drug alternative would not be as effective or better than the adopted three-drug procedure."
The challenge decided by the state court was filed in August 2010 on behalf of inmate Michael Sims, who has been on death row for more than 20 years, according to his attorney Sara Eisenberg. She summarized the decision by saying that the current regulations approving the use of the three-drug mix "are invalid."
She said a similar case being argued in federal court calls the three-drug process cruel and unusual punishment. That case is not expected to be heard until 2012.
A spokeswoman for the California Department of Corrections and Rehabilitation, Terry Thornton, said the department will withhold comment until it gets a copy of the final ruling.
Executions have been on hold since 2006 in California after a federal judge ruled the state's lethal-injection method unconstitutional. More than 700 people are on death row in the state.
CNN's Greg Morrison contributed to this story